Experimental Study On A Domestic Multifunctional Solar Assisted Heat Pump System

Solar water heater, a kind of energy-saving and environmental protection product, utilizes the solar energy for water heating. It needs an assistant heat source to put it into use when there is no solar irradiation available. Air source heat pump water heater (ASHPWH) absorbs heat from air for water heating with heat pump principle. It is not economic to use ASHPWH just for water heating because of its high cost, which hampers its popularization. Domestic air conditioner can be used widely, but it doesn't work in most time of the year.In order to take advantages of the above three products and make up their deficiency, a novel system was proposed which is called domestic multifunctional solar assisted heat pump (DMSAHP). The DMSAHP can work in the following six different modes: solar water heating, heat pump water heating, space cooling and water heating, air source heat pump space heating and water source heat pump space heating. The system not only can take full use of the solar energy for water heating but also can operate heat pump water heating mode as an assistant mode to get hot water. The energy utilization ratio is high in the space cooling integrated water heating mode because this mode can be used for space cooling and can recover the condensation heat energy for water heating at the same time. The water source heat pump space heating mode can obtain energy from the hot water heated by solar energy for space heating, which is able to improve the capacity of space heating and the utilization ratio of solar energy.Firstly, the principle and different operating modes of the DMSAHP are presented, and a prototype of the DMSAHP is designed. The model of the DMSAHP system was built. Considering the practicability and easiness to install and maintain, we separate the integrated system into four parts: outdoor unit, indoor unit, solar hot water system and hot water tank.Secondly, the operating performances of the heat pump water heating mode, space cooling integrated water heating mode, air source heat pump space heating mode and water source heat pump space heating mode have been studied. The results show that these five modes of the DMSAHP can be operated stably and reliably.The tests of the prototype of the DMSAHP in water heating mode were conducted under different work conditions. The coefficient of performance (COP) can reach 5.05kW/kW, and the COP under the lowest ambient temperature, 7℃, ranges from 1.63kW/kW to 4.96kW/kW. The results indicate that the DMSAHP can save energy efficiently in water heating mode.The experimental studies of the prototype of the DMSAHP in space cooling mode and space cooling integrated water heating mode were conducted under specified space cooling work condition. The total cooling capacity and the energy efficiency ratio (EER) in space cooling mode are 4.981kW and 2.61kW/kW respectively. The combined EER in the space cooling integrated water heating mode ranges from 3.39 kW/ kW to 6.20 kW/ kW.The tests of the prototype of the DMSAHP in air source heat pump space heating mode and water source heat pump space heating mode were conducted under specified space heating work condition. The heating capacity and the in air source heat pump space heating mode are 4.938kW and 2.77 kW/kW respectively. The heating capacity in water source heat pump space heating mode ranges from 5.758kW to 9.105kW, and the COP in this mode ranges from 3.18 kW/ kW to 3.69 kW/ kW.The DMSAHP is a complex system which consists of many parts and can operate in many different modes. To make the DMSAHP system operating automatically, an automatic control programme has been presented.